Chapter 13 - Effect of Internal and External Factors on Root Growth and Development

Abstract

Publisher Summary This chapter describes the role played by various internal and external factors in root growth and development. Root growth and development consist of the initiation, elongation, and development of new root axes, and they are regulated by plant hormones. Root architecture responds to the soil environment by changing growth and branching patterns, and the differences in plant hormone synthesis and response probably mediate these plastic responses to the environment as well as contribute to genetic differences in root architecture and plasticity. Root growth and development depend on an adequate supply of carbohydrates from current photosynthesis or stored reserves. Therefore, various environmental conditions that affect photosynthesis, including water availability, temperature, light intensity, and nutrient availability may influence root growth by affecting carbohydrate supply to the roots. Nutrient supply can strongly affect root growth, morphology, and distribution of root systems in the substrate and this effect is particularly marked with N, less distinct with P, and usually absent with other nutrients, except Mg. Soil organisms, which include microorganisms, mesofauna, and macrofauna, can stimulate or inhibit root growth as they play a critical role in nutrient cycling by mineralizing organic compounds into inorganic nutrients or transforming nutrients that can then be taken up by plants. They may also affect root growth by releasing stimulating or inhibiting compounds, root damage or, in case of larger soil organisms such as earthworms, by creating pores, which improve drainage and aeration as well as provide pathways for roots.